The present invention relates to pressure molding and relates in particular to distribution manifold systems termed "hot runners" for supplying hot flowable plastic material to a number of mold cavities via nozzles under conditions of controlled pressure and temperature and with substantially uniform flow rates, thereby creating uniform quality molded products in each of the mold cavities.
Unavoidable differences between the temperatures of the individual elements of such systems, start-up temperature transitions, time to stabilize temperatures and the thermal characteristics of the system components create problems of thermal expansion differences which lead to misalignment and plastic material leaks between the components, as well as mechanical damage, which can be minimized only at great expense by finishing and assembling them with extreme accuracy.
Frequently the manifolds are supported movably (termed "floating") to accommodate differential thermal expansion while preserving a seal between the channels within the manifold and channels from the manifold to the mold cavities through nozzles; and also while providing sufficient support of the manifold during operation.
A prior art floating manifold is disclosed and described in U.S. Pat. No. 4,333,629, issued June 8, 1982 to S. S. Roy entitled Floating Manifold for Multi-Cavity Injection Mold.
In the '629 reference the manifold 16 makes a telescopic or sliding fit with a supply tube 30 received in manifold inlet 22 to allow for thermal expansion along the supply tube. Correspondingly the discharge side of the manifold makes a sliding fit with the mold cavities in that delivery tubes 56 float relative to mating cavities.